Waveguide



June 11, 1968 D. RAMONAT 3,388,352

WAVEGUIDE Filed Feb. 25, 1966 5 Sheets-Sheet 1 IFIG.I.

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WAVEGUIDE Filed Feb. 25. 1966 3 Sheets-Sheet :5

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. ATIQBNEZS United States Patent 3,388,352 WAVEGUIDE Dieter Ramonat, Backnang, Germany, assignor to Telefunken Patentverwertungsgesellschaft m.b.H., Ulm, Germany Filed Feb. 25, 1966, Ser. No. 530,034 Claims priority, application Germany, Feb. 25, 1965,

8 Claims. (Cl. 333-98) The present invention relates to a broadband, low reflection waveguide transition member for the connection of a rectangular waveguide and a substantially elliptical corrugated flexible waveguide.

Transition members, generally used for connection between rectangular and elliptical waveguides, are generally constructed, for example, as AA stepped transformation members or as continuous transitions, and can often only be produced for narrow bandwidths, and at that only with great mechanical expenditure due to the difierent disposition characteristics in rectangular and elliptical corrugated waveguides. In the continuous transition members heretofore used, which connect a rectangular waveguide to an elliptical one, the geometrical shape of the inner surface of the transition member was generally obtained by the intersection of a cylinder or a pyramid by a member having a rectangular cross-section, or by the intersection of a cone and a member having an elliptical cross-section, with the major axis in either case being the same. However, no single transition member serves for all connection purposes and appropriate transition members must be provided in each case for the connection of two waveguides having different cross-sectional shapes and cross-sectional areas.

The inner surface of the waveguide transition members is generally produced by means of an electroplating method or by casting. The cores necessary for this, which first have to be cast in complicated molds, have an extremely short useful life in that these cores often have to be destroyed on removal from the formed transition member. Recently, however, elliptical milling machines have been developed and are used in order to shorten the very tedious production and thereby somewhat reduce the expense of such transition members. However, the production cost of such a transition member is still high. Another disadvantage in prior art transition members is that such members have a relatively high reflection factor, for example, r=4%, and a very low relative bandwidth.

It is therefore an object of the present invention to provide a waveguide transition member which is mechanically easy to produce and therefore more economical to produce.

It is another object of the present invention to provide a waveguide transition member having a short structural length and a very low reflection factor while including a relatively wide bandwidth.

According to the present invention, the disadvantages of prior art arrangements are overcome by providing a waveguide transition member for the connection of a rectangular waveguide to an elliptical corrugated waveguide wherein the transition member is formed as a portion of the rectangular waveguide.

According to a feature of the present invention, the rectangular waveguide is joined to an elliptical corrugated waveguide with the transition between such waveguides being compensated for by providing a tapered recess in the rectangular waveguide and the provision of tuning screws within the tapered portion.

Additional objects and advantages of the present invention will become apparent upon consideration of the following description when taken in conjunction with the accompanying drawings in which:

3,388,352 Patented June 11, 1968 FIGURE 1 is a perspective view of a prior art transition member.

FIGURE 2 is a perspective view of another prior art transition member,

FIGURE 3 is a perspective view of a rectangular waveguide and an elliptical waveguide according to the present invention.

FIGURE 4 is a perspective view partly in cross-section of a transition member constructed according to the present invention.

FIGURE 5 is a fragmentary perspective view, partly in cross-section, of a further embodiment of a transition member.

FIGURES 6a-6c illustrate curves showing the locus of the reflection factor for waveguide transition members produced according to the-present invention.

FIGURE 7 is an end view of a diaphragm for use with the transition member according to the present invention.

Referring now to the drawings, there is shown in FIG- URES 1 and 2 a prior art transition member wherein the geometrical shape of the inner surface was formed by the intersection of a cylinder or a pyramid with a member having a rectangular cross-section, or by the intersection of a cone and a member having an elliptical cross-section. However, as shown, in either case the major axis for the formed transition member is the same. As is further shown, the inner waveguide surface of the transition member has cross-sectional areas of varying size. In fact, very often, the smallest cross-sectional area designated by reference character 3, in FIGURE 2, lies between the elliptical crosssectional plane 1 and the rectangular cross-sectional plane 2. However, as stated previously, different transition members must be provided for the differing connection purposes.

FIGURE 3 shows a rectangular waveguide 5 having a standard cross-section and positioned for directly abutting an elliptical corrugated waveguide 6 so as to be joined thereto at the end 7 of the rectangular waveguide. According to the present invention, the rectangular waveguide serves as the transition member by providing the waveguide with means to compensate for the change in impedance which occurs at the joint between the two waveguides. Thus, in accordance with the present invention, a waveguide transition member is formed which is mechanically easy to produce and which has a very low reflection factor and a relatively wide bandwidth. Furthermore, the waveguide transition member is provided with a short structural length since the rectangular waveguide 5 directly abuts the elliptical waveguide 6 and serves as the transition member.

Referring to FIGURE 4, there is shown the rectangular waveguide and transition member according to the present invention. The change in impedance at the joint of the waveguides is compensated for by means which include tapered recesses 9a and 9b provided in the more closely spaced parallel inner surfaces of the rectangular waveguide. Thus, the upper and lower surfaces which are more closely spaced than the side surfaces are enlarged by the axially symmetrical tapered recesses which widen in the direction of the elliptical waveguide 6 and which have an angle of inclination a which is preferably constant. The angle of inclination a varies between 2 and 12 while the tapered widening preferably extends the length of wherein is the wavelength of the rectangular waveguide.

The change in impedance at the joint 7 is further compensated by providing compensating members in the form of two or three tuning screws disposed within the tapered widening portion of the rectangular waveguide. A first tuning screw 11 is provided at the joint of the rectangular and elliptical waveguides with the arrangement and spacing of a second tuning screw 13 within the tapered portion, depending upon the cross-sectional relationship between the elliptical and rectangular waveguides and on the frequency. The spacing of the second tuning screw may vary between MM and VM with the compensating member preferably being disposed at the VM position. In order that large manufacturing tolerances may be permitted, as shown in FIGURE 5, the tuning screw 13 may be replaced with two tuning screws 13' and 13", with these screws being arranged within the tapered recess 9a and in close proximity to each other. The manufacturing tolerances for the rectangular waveguide transition member may be further increased at the aperture plane 15 of the waveguide, which aperture plane is provided with a rectangular cross-section by spacing the tapered recesses 9a and 9b from the aperture plane so that the recesses begin after a so-called calming length 19.

Thus, by use of the transition member according to the present invention, i.e., providing tapered circular recesses in the rectangular waveguide, it is possible to produce the transition member either by turning, or casting, or by an electroplating process. Furthermore, the preparation of the necessary cores for the manufacture of such transition members does not present any difiiculties and, in addition, these cores due to the structure of the transition member can be used repeatedly.

Referring now to FIGURES 6, there are illustrated curves showing for instance the locus of the reflection factor for three mass-produced waveguide transition members according to the present invention. The dashed-line circles define a reflection factor r of 1% and from these figures it can be seen that the reflection factor r is less than 1% for the mass-produced waveguides. The relative bandwidth Af/f amounts to :8% with this reflection factor.

FIGURE 7 shows a device for use with the present invention when the cross-section of the rectangular waveguide is equal to or greater than the cross-section of the corrugated elliptical waveguide to be connected thereto. When the rectangular waveguide cross-section is larger, the electrically effective cross-section of the waveguide may be reduced by means of a diaphragm 21. The diaphragm serves to reduce the electrically elfective crosssection at the joint between the two waveguide portions and, as shown, the diaphragm aperture 23 is preferably formed from intersecting arcs, although any suitable shape may be chosen. The diaphragm 21 is positioned between the rectangular waveguide and the corrugated waveguide at the joint thereof and has a thickness which is relatively small with respect to h It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

What is claimed is:

1. A broadband waveguide transition member having low reflection, for the connection of a corrugated waveguide having a substantially elliptical cross-section to a rectangular waveguide, comprising in combination:

a rectangular waveguide for directly abutting a corrugated elliptical waveguide, said rectangular waveguide forming the transition member and including two pairs of spaced parallel inner surfaces arranged transversely to each other with one of said pair of surfaces being spaced more closely than the other pair, each of said closely spaced surfaces being provided with an axially symmetrical tapered recess, said tapered recesses enlarging in the direction of the elliptical waveguide and extending wherein A is the wavelength of the rectangular waveguide, and said tapered recesses being provided with a constant inclination angle which lies between 2 and 12;

compensating members disposed within at least one of said tapered recesses and one of said members being provided at the abutting end of said rectangular waveguide, whereby said tapered recesses and said compensating members effect a matching of the properties of the rectangular and elliptical waveguides.

2. A transition member as defined in claim 1 wherein said compensating members are tuning screws.

3. A transition member as defined in claim 1 wherein said rectangular waveguide is provided with an aperture plane and said tapered recesses are spaced from said aperture plane by a so-called calming length distance.

4. A transition member as defined in claim 1 wherein two compensating members are provided and the spacing between said two members varies between MM and 12% with the spacing being dependent on the crosssectional relationship between the elliptical and rectangular waveguides.

5. A transition member as defined in claim 1 wherein three compensating members are provided, two of said compensating members being arranged in close proximity and the spacing between said two members and said other member varies between AA and /zx with the spacing being dependent on the cross-sectional relationship between the elliptical and rectangular waveguides.

6. A transition member as defined in claim 1 and further comprising a flexible corrugated waveguide having a substantially elliptical cross-section, said rectangular waveguide directly abutting and being joined to said elliptical waveguide.

7. A transition member as defined in claim 6 wherein the cross-section of said rectangular waveguide is equal to or greater than the cross-section of the corrugated waveguide, and a diaphragm is provided for reducing the electrically-effective cross-section of the rectangular waveguide at the joint between said rectangular and said elliptical waveguides.

8. A transition member as defined in claim 7 wherein the aperture of said diaphragm is formed from intersecting arcs.

References Cited UNITED STATES PATENTS 3,300,741 1/1967 Hersch et al. 33355 3,336,543 8/1967 Johnson et al. a. 333- FOREIGN PATENTS 1,099,602 2/ 1961 Germany.

ELI LIEBERMAN, Primary Examiner. L. ALLAHUT, Assistant Examiner. 

1. A BROADBAND WAVEGUIDE TRANSITION MEMBER HAVING LOW REFLECTION, FOR THE CONNECTION OF A CORRUGATED WAVEGUIDE HAVING A SUBSTANTIALLY ELLIPTICAL CROSS-SECTION TO A RECTANGULAR WAVEGUIDE, COMPRISING IN COMBINATION: A RECTANGULAR WAVEGUIDE FOR DIRECTLY ABUTING A CORRUGATED ELLIPTICAL WAVEGUIDE, SAID RECTANGULAR WAVEGUIDE FORMING THE TRANSITION MEMBER AND INCLUDING TWO PAIRS OF SPACED PARALLEL INNER SURFACES ARRANGED TRANSVERSELY TO EACH OTHER WITH ONE OF SAID PAIR OF SURFACES BEING SPACED MORE CLOSELY THAN THE OTHER PAIR, EACH OF SAID CLOSELY SPACED SURFACES BEING PROVIDED WITH AN AXIALLY SYMMETRICAL TAPERED RECESS, SAID TAPERED RECESSES ENLARGING IN THE DIRECTION OF THE ELLIPTICAL WAVEGUIDE AND EXTENDING 3/4$HR WHEREIN $HR IS THE WAVELENGTH OF THE RECTANGULAR WAVEGUIDE, AND SAID TAPERED RECESSES BEING PROVIDED WITH A CONSTANT INCLINATION ANGLE WHICH LIES BETWEEN 2* AND 12*; 